U.S. patent number 7,013,876 [Application Number 11/094,516] was granted by the patent office on 2006-03-21 for fuel injector control system.
This patent grant is currently assigned to Caterpillar Inc.. Invention is credited to W. John Love, Daniel R. Puckett.
United States Patent |
7,013,876 |
Puckett , et al. |
March 21, 2006 |
Fuel injector control system
Abstract
A control system for a fuel injector is disclosed. The control
system has a valve element movable between a first position and a
second position, an armature connected to the valve element, a
solenoid configured to move the armature and connected valve
element, and a controller in communication the solenoid. The
controller is configured to energize the solenoid at a first
current level to initiate movement of the valve element from the
first position toward the second position, at a second current
level less than the first current level during movement of the
valve element from the first position toward the second position,
at a third current level less than the second current level after
the valve element has reached the second position, and at a fourth
current level less than the third current level after the valve
element has been in the second position for a predetermined period
of time.
Inventors: |
Puckett; Daniel R. (Peoria,
IL), Love; W. John (Dunlap, IL) |
Assignee: |
Caterpillar Inc. (Peoria,
IL)
|
Family
ID: |
36045383 |
Appl.
No.: |
11/094,516 |
Filed: |
March 31, 2005 |
Current U.S.
Class: |
123/490;
361/154 |
Current CPC
Class: |
F02D
41/20 (20130101); F02D 2041/2006 (20130101); F02D
2041/2017 (20130101); F02D 2041/2037 (20130101); F02D
2041/2041 (20130101) |
Current International
Class: |
F02M
51/00 (20060101) |
Field of
Search: |
;123/472,478,490
;361/154 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Solis; Erick
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner LLP
Claims
What is claimed is:
1. A control system for a fuel injector, comprising: a valve
element movable between a first position and a second position; an
armature connected to the valve element; a solenoid configured to
move the armature and connected valve element; and a controller in
communication the solenoid, the controller configured to: energize
the solenoid at a first current level to initiate movement of the
valve element from the first position toward the second position,
thereby initiating an injection of fuel; energize the solenoid at a
second current level less than the first current level during
movement of the valve element from the first position toward the
second position; energize the solenoid at a third current level
less than the second current level after the valve element has
reached the second position; energize the solenoid at a fourth
current level less than the third current level after the valve
element has been in the second position for a predetermined period
of time; and de-energize the solenoid to return the valve element
to the first position, thereby stopping the injection of fuel.
2. The control system of claim 1, wherein the controller is further
configured to energize the solenoid at a fifth current level less
than the third current level to slow the valve element during
movement from the first position toward the second position.
3. The control system of claim 2, wherein the controller is
configured to energize the solenoid at the fifth current level
after energizing the valve element at the second current level and
before energizing the valve element at the third current level,
during a single injection event.
4. The control system of claim 1, wherein the controller is further
configured to determine the time from the end of a first injection
to the start of a subsequent injection and to increase the
magnitude of at least one of the first and second current levels of
the subsequent injection if the determined time is less than a
predetermined time.
5. The control system of claim 4, wherein the controller is further
configured to decrease the duration during which the solenoid is
energized to at least one of the first and second current levels of
the subsequent injection if the determined time is less than a
predetermined time.
6. The control system of claim 1, wherein the second current level
corresponds to a battery-induced current level.
7. The control system of claim 6, wherein the first current level
is greater than the battery-induced current level.
8. The control system of claim 1, wherein the controller is further
configured to energize the solenoid at a fifth current level during
movement of the valve element from the second position toward the
first position to slow the valve element.
9. The control system of claim 8, wherein the controller is further
configured to determine a desired dampening associated with the
valve element moving from the second position toward the first
position and to compare the desired dampening to a predetermined
dampening level, the fifth current level being a
freewheeling-generated current level when the desired dampening is
less than the predetermined dampening level and a current level
greater than a battery-induced current level when the desired
dampening is greater than a predetermined dampening level.
10. The control system of claim 1, further including a freewheeling
circuit configured to generate a current from the interaction of
the solenoid and the armature during movement of the valve element
from the second position toward the first position.
11. The control system of claim 10, wherein the current generated
by the freewheeling circuit is also used to indicate a relative
position of the valve element to a seat.
12. A method of controlling a fuel injector having a solenoid and
an armature connected to a valve element movable between a first
and second position, the method comprising: energizing the solenoid
at a first current level to initiate movement of the valve element
from the first position toward the second position, thereby
initiating an injection of fuel; energizing the solenoid at a
second current level less than the first current level during
movement of the valve element from the first position toward the
second position; energizing the solenoid at a third current level
less than the second level after the valve element has reached the
second position; energizing the solenoid at a fourth current level
less than the third current level after the valve element has been
in the second position for a predetermined period of time, and
de-energizing the solenoid to return the valve element to the first
position, thereby stopping the injection of fuel.
13. The method of claim 12, further including energizing the
solenoid at a fifth current level less than the third current level
to slow the valve element during movement from the first position
toward the second position.
14. The method of claim 13, wherein energizing the solenoid at the
fifth current level includes energizing the solenoid at the fifth
current level after energizing the valve element at the second
current level and before energizing the valve element at the third
current level, during a single injection event.
15. The method of claim 12, further including: determining the time
from the end of a first injection to the start of a subsequent
injection; and increasing the magnitude of at least one of the
first and second current levels of the subsequent injection if the
determined time is less than a predetermined time.
16. The method of claim 15, further including decreasing the
duration during which the solenoid is energized to at least one of
the first and second current levels of the subsequent injection if
the determined time is less than a predetermined time.
17. The method of claim 12, wherein the second current level
corresponds to a battery-induced current level.
18. The method of claim 17, wherein the first current level is
greater than the battery-induced current level.
19. The method of claim 12, further including energizing the
solenoid at a fifth current level during movement of the valve
element from the second position toward the first position to slow
the valve element.
20. The method of claim 19, further including: determining a
desired dampening associated with the valve element moving from the
second position toward the first position; and comparing the
desired dampening to a predetermined dampening level, wherein the
fifth current level is a freewheeling-generated current level when
the desired dampening is less than the predetermined dampening
level and a current level greater than a battery-induced current
level when the desired dampening is greater than the predetermined
dampening level.
21. The method of claim 12, further including generating a current
from the interaction of the solenoid and the armature during
movement of the valve element from the second position toward the
first position.
22. The method of claim 21, further including determining a
relative position of the valve element to a seat based on the
generated current.
23. A fuel system for an engine having at least one combustion
chamber, the fuel system comprising: a source of pressurized fuel;
at least one fuel injector configured to inject the pressurized
fuel into the at least one combustion chamber, the fuel injector
including: a solenoid; an armature movable by the solenoid; and a
valve element fixedly connected to the armature, wherein movement
of the valve element from a first position toward a second position
initiates injection of pressurized fuel into the at least one
combustion chamber; and a control system, including a controller in
communication with the solenoid, the controller being configured
to: energize the solenoid at a first current level to initiate
movement of the valve element from the first position toward the
second position, thereby initiating an injection of fuel, the first
current level being greater than a battery-induced current level;
energize the solenoid at the battery-induced current level during
movement of the valve element from the first position toward the
second position; energize the solenoid at a third current level
less than the battery-induced current level after the valve element
has reached the second position; energize the solenoid at a fourth
current level less than the third current level after the valve
element has been in the second position for a predetermined period
of time; and de-energize the solenoid to return the valve element
to the first position, thereby stopping the injection of fuel.
24. The fuel system of claim 23, wherein the controller is further
configured to energize the solenoid at a fifth current level after
energizing the valve element at the battery-induced current level
and before energizing the valve element at the third current level
to slow the valve element during movement from the first position
toward the second position, the fifth current level being less than
the third current level.
25. The fuel system of claim 23, wherein the controller is further
configured to determine the time from the end of a first injection
to the start of a subsequent injection and to increase the
magnitude of at least one of the first current level and the
battery-induced current level of the subsequent injection if the
determined time is less than a predetermined time.
26. The fuel system of claim 25, wherein the controller is further
configured to decrease the duration during which the solenoid is
energized to at least one of the first current level and the
battery-induced current level of the subsequent injection if the
determined time is less than the predetermined time.
27. The fuel system of claim 23, wherein the controller is further
configured to energize the solenoid at a fifth current level during
movement of the valve element from the second position toward the
first position to slow the valve element.
28. The fuel system of claim 27, wherein the controller is further
configured to determine a desired dampening associated with the
valve element moving from the second position toward the first
position and to compare the desired dampening to a predetermined
dampening level, the fifth current level being a
freewheeling-generated current level when the desired dampening is
less than the predetermined dampening level and a first current
level greater than a battery-induced current level when the desired
dampening is greater than a predetermined dampening level.
29. The fuel system of claim 23, further including a freewheeling
circuit configured to generate a current from the interaction of
the solenoid and the armature during movement of the valve element
from the second position toward the first position, the controller
further configured to determine a relative position of the valve
element to a seat based on the generated current.
Description
TECHNICAL FIELD
The present disclosure is directed to a control system and, more
particularly, to a control system for a fuel injector.
BACKGROUND
Common rail fuel injectors provide a way to introduce fuel into the
combustion chamber of an engine. Typical common rail fuel injectors
include an actuating solenoid that opens a fuel injector nozzle
when the solenoid is energized. Fuel is then injected into the
combustion chamber as a function of the time period during which
the solenoid remains energized. Accurate control of both the
delivery timing and duration of fuel is important to engine
performance and emissions.
To optimize engine performance and emissions, engine manufacturers
may vary the times when the solenoid is energized and de-energized,
as well as the magnitude of the current applied to the solenoid.
One such example is described in U.S. Pat. No. 4,922,878 (the '878
patent) issued to Shinogle et al. on May 8, 1990. The '878 patent
describes a solenoid control circuit that controls actuation of an
injector control valve. The solenoid control circuit provides a
three tier current waveform having a pull-in current level, a
hold-in current level, and an intermediate current level.
Energizing the solenoid at the pull-in level starts movement of the
control valve and the flow of fuel to the engine. After the control
valve starts to move, the current level is reduced to the
intermediate level, which is less than the pull-in current level
but great enough to continue movement of the control valve. The
applied current is then further reduced to the hold-in level to
hold the control valve at the moved position. The solenoid may then
be de-energized to return the control valve to its initial position
to stop the flow of fuel to the engine.
Although the solenoid control circuit of the '878 patent may
sufficiently inject fuel into an engine, it may do little to
minimize bouncing of the control valve and the resulting effects.
In particular, due to inertia of the moving control valve and the
associated fuel, upon fully opening, the control valve may tend to
bounce away from an upper seat, thereby adversely affecting fuel
delivery characteristics. Because the hold-in current of the '878
patent is single tiered, it may be insufficient to fully minimize
control valve bouncing. Alternatively, if the hold-in current of
the '878 patent is sufficient to minimize control valve bouncing,
it may be inefficient for holding the control valve at the moved
position after the tendency to bounce has decreased. In addition,
the '878 patent does not adjust the tier levels to accommodate the
effects of bouncing between closely coupled injections or dampen
the closing movements of the control valve to minimize the
likelihood of return bouncing.
The control system of the present disclosure solves one or more of
the problems set forth above.
SUMMARY OF THE INVENTION
One aspect of the present disclosure is directed to a control
system for a fuel injector. The control system includes a valve
element movable between a first position and a second position, and
an armature connected to the valve element. The control system
includes a solenoid configured to move the armature and connected
valve, and a controller in communication with the solenoid. The
controller is configured to energize the solenoid at a first
current level to initiate movement of the valve element from the
first position toward the second position, thereby initiating an
injection of fuel. The controller is also configured to energize
the solenoid at a second current level less than the first current
level during movement of the valve element from the first position
toward the second position and to energize the solenoid at a third
current level less than the second current level after the valve
element has reached the second position. The controller is further
configured to energize the solenoid at a fourth current level less
than the third current level after the valve element has been in
the second position for a predetermined period of time and to
de-energize the solenoid to return the valve element to the first
position, thereby stopping the injection of fuel.
Another aspect of the present disclosure is directed to a method of
controlling a fuel injector having a solenoid and an armature
connected to a valve element movable between a first position and a
second position. The method includes energizing the solenoid at a
first current level to initiate movement of the valve element from
the first position toward the second position, thereby initiating
an injection of fuel. The method also includes energizing the
solenoid at a second current level less than the first current
level during movement of the valve element from the first position
toward the second position and energizing the solenoid at a third
current level less than the second current level after the valve
element has reached the second position. The method further
includes energizing the solenoid at a fourth current level less
than the third current level after the valve element has been in
the second position for a predetermined period of time and
de-energizing the solenoid to return the valve element to the first
position, thereby stopping the injection of fuel.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic and diagrammatic illustration of an exemplary
disclosed fuel system;
FIG. 2 is a cross-sectional illustration of an exemplary disclosed
fuel injector for the fuel system of FIG. 1;
FIG. 3A is a control diagram for the fuel injector of FIG. 2;
FIG. 3B is another control diagram for the fuel injector of FIG.
2;
FIG. 4 is a flow chart depicting an exemplary method of operating
the fuel injector of FIG. 2; and
FIG. 5 is a flow chart depicting another exemplary method of
operating the fuel injector of FIG. 2.
DETAILED DESCRIPTION
FIG. 1 illustrates an engine 10 and an exemplary embodiment of a
fuel system 12. For the purposes of this disclosure, engine 10 is
depicted and described as a four-stroke diesel engine. One skilled
in the art will recognize, however, that engine 10 may be any other
type of internal combustion engine such as, for example, a gasoline
or a gaseous fuel-powered engine. Engine 10 may include an engine
block 14 that defines a plurality of cylinders 16, a piston 18
slidably disposed within each cylinder 16, and a cylinder head 20
associated with each cylinder 16.
Cylinder 16, piston 18, and cylinder head 20 may form a combustion
chamber 22. In the illustrated embodiment, engine 10 includes six
combustion chambers 22. However, it is contemplated that engine 10
may include a greater or lesser number of combustion chambers 22
and that combustion chambers 22 may be disposed in an "in-line"
configuration, a "V" configuration, or any other suitable
configuration.
As also shown in FIG. 1, engine 10 may include a crankshaft 24 that
is rotatably disposed within engine block 14. A connecting rod 26
may connect each piston 18 to crankshaft 24 so that a sliding
motion of piston 18 within each respective cylinder 16 results in a
rotation of crankshaft 24. Similarly, a rotation of crankshaft 24
may result in a sliding motion of piston 18.
Fuel system 12 may include components that cooperate to deliver
injections of pressurized fuel into each combustion chamber 22.
Specifically, fuel system 12 may include a tank 28 configured to
hold a supply of fuel, a fuel pumping arrangement 30 configured to
pressurize the fuel and direct the pressurized fuel to a plurality
of fuel injectors 32 by way of a common rail 34, and a control
system 35.
Fuel pumping arrangement 30 may include one or more pumping devices
that function to increase the pressure of the fuel and direct one
or more pressurized streams of fuel to common rail 34. In one
example, fuel pumping arrangement 30 includes a low pressure source
36 and a high pressure source 38 disposed in series and fluidly
connected by way of a fuel line 40. Low pressure source 36 may be a
transfer pump configured to provide low pressure feed to high
pressure source 38. High pressure source 38 may be configured to
receive the low pressure feed and to increase the pressure of the
fuel to the range of about 30 300 MPa. High pressure source 38 may
be connected to common rail 34 by way of a fuel line 42. A check
valve 44 may be disposed within fuel line 42 to provide for
one-directional flow of fuel from fuel pumping arrangement 30 to
common rail 34.
One or both of low pressure and high pressure sources 36, 38 may be
operably connected to engine 10 and driven by crankshaft 24. Low
and/or high pressure sources 36, 38 may be connected with
crankshaft 24 in any manner readily apparent to one skilled in the
art where a rotation of crankshaft 24 will result in a
corresponding rotation of a pump drive shaft. For example, a pump
driveshaft 46 of high pressure source 38 is shown in FIG. 1 as
being connected to crankshaft 24 through a gear train 48. It is
contemplated, however, that one or both of low and high pressure
sources 36, 38 may alternatively be driven electrically,
hydraulically, pneumatically, or in any other appropriate
manner.
Fuel injectors 32 may be disposed within cylinder heads 20 and
connected to common rail 34 by way of a plurality of fuel lines 50.
Each fuel injector 32 may be operable to inject an amount of
pressurized fuel into an associated combustion chamber 22 at
predetermined timings, fuel pressures, and fuel flow rates. The
timing of fuel injection into combustion chamber 22 may be
synchronized with the motion of piston 18. For example, fuel may be
injected as piston 18 nears a top-dead-center position in a
compression stroke to allow for compression-ignited-combustion of
the injected fuel. Alternatively, fuel may be injected as piston 18
begins the compression stroke heading towards a top-dead-center
position for homogenous charge compression ignition operation. Fuel
may also be injected as piston 18 is moving from a top-dead-center
position towards a bottom-dead-center position during an expansion
stroke for a late post injection to create a reducing atmosphere
for aftertreatment regeneration.
Control system 35 may control operation of each fuel injector 32.
In particular, control system 35 may include a controller 53 that
communicates with fuel injectors 32 by way of a plurality of
communication lines 51. Controller 53 may be configured to control
a fuel injection timing, amount, and duration by applying a
predetermined current waveform or sequence of current waveforms to
each fuel injector 32.
Controller 53 may embody in a single microprocessor or multiple
microprocessors that include a means for controlling an operation
of fuel injector 32. Numerous commercially available
microprocessors can be configured to perform the functions of
controller 53. It should be appreciated that controller 53 could
readily embody a general work machine or engine microprocessor
capable of controlling numerous work machine or engine functions.
Controller 53 may include all the components required to run an
application such as, for example, a memory, a secondary storage
device, and a processor, such as a central processing unit or any
other means known in the art for controlling fuel injectors 32.
Various other known circuits may be associated with controller 53,
including power supply circuitry, signal-conditioning circuitry,
solenoid driver circuitry, communication circuitry, and other
appropriate circuitry.
As illustrated in FIG. 2, each fuel injector 32 may be a closed
nozzle unit fuel injector. Specifically, each fuel injector 32 may
include an injector body 52, a housing 54 operably connected to
injector body 52, a guide 55 disposed within housing 54, a nozzle
member 56, a needle valve element 58, and a solenoid actuator 59.
It is contemplated that additional components may be included
within fuel injector 32 such as, for example, restricted orifices,
pressure-balancing passageways, accumulators, and other injector
components known in the art.
Injector body 52 may embody a cylindrical member configured for
assembly within cylinder head 20 and having one or more
passageways. Specifically, injector body 52 may include a central
bore 100 configured to receive solenoid actuator 59, a fuel inlet
102 and fuel outlet 104 in communication with central bore 100, and
a control chamber 106. Control chamber 106 may be in communication
with central bore 100 via a control passageway 108 and in direct
communication with needle valve element 58. Control chamber 106 may
be selectively drained of or supplied with pressurized fuel to
affect motion of needle valve element 58. Injector body 52 may also
include a supply passageway 110 that fluidly communicates central
bore 100 with nozzle member 56.
Housing 54 may embody a cylindrical member having a central bore 60
for receiving guide 55 and nozzle member 56, and an opening 62
through which a tip end 64 of nozzle member 56 protrudes. A sealing
member such as, for example, an o-ring (not shown) may be disposed
between guide 55 and nozzle member 56 to restrict fuel leakage from
fuel injector 32.
Guide 55 may also embody a cylindrical member having a central bore
68 configured to receive needle valve element 58 and a return
spring 90. Return spring 90 may be disposed between a stop 92 and a
seating surface 94 to axially bias needle valve element 58 toward
tip end 64. A spacer 96 may be disposed between return spring 90
and seating surface 94 to reduce wear of the components within fuel
injector 32. It is contemplated that an additional spacer (not
shown) may be disposed between return spring 90 and stop 92 to
further reduce component wear.
Nozzle member 56 may likewise embody a cylindrical member having a
central bore 72 and a pressure chamber 71. Central bore 72 may be
configured to receive needle valve element 58. Pressure chamber 71
may hold pressurized fuel supplied from supply passageway 110 in
anticipation of an injection event. Nozzle member 56 may also
include one or more orifices 80 to allow the pressurized fuel to
flow from pressure chamber 71 through central bore 72 into
combustion chambers 22 of engine 10, as needle valve element 58 is
moved away from orifices 80.
Needle valve element 58 may be an elongated cylindrical member that
is slidingly disposed within guide 55 and nozzle member 56. Needle
valve element 58 may be axially movable between a first position at
which a tip end of needle valve element 58 blocks a flow of fuel
through orifices 80, and a second position at which orifices 80 are
open to allow a flow of fuel into combustion chamber 22. It is
contemplated that needle valve member 58 may be a multi-member
element having a needle member and a piston member or a single
integral element.
Needle valve element 58 may have multiple driving hydraulic
surfaces. For example, needle valve element 58 may include a
hydraulic surface 112 tending to drive needle valve element 58,
with the bias of return spring 90, toward a first or
orifice-blocking position when acted upon by pressurized fuel.
Needle valve element 58 may also include a hydraulic surface 114
that opposes the bias of return spring 90 to drive needle valve
element 58 in the opposite direction toward a second or
orifice-opening position when acted upon by pressurized fuel.
Solenoid actuator 59 may be disposed opposite nozzle member 56 to
control the forces on needle valve element 58. In particular
solenoid actuator 59 may include windings 116 of a suitable shape
through which current may flow to establish a magnetic field.
Solenoid actuator 59 may also include an armature 118 fixedly
connected to a two-position control valve element 120. When
energized, the magnetic field established by windings 116 may urge
armature 118 and connected control valve element 120 against the
bias of a return spring 123 from a first or non-injecting position
to a second or injecting position. For example, control valve
element 120 may be moved between a lower seat 122 and an upper seat
124. In the non-injecting position, fuel may flow from fuel inlet
102 through control passageway 108 into control chamber 106. As
pressurized fuel builds within control chamber 106, the downward
force generated at hydraulic surface 112 combined with the force of
return spring 90 may overcome the upward force at hydraulic surface
114, thereby closing orifices 80 and terminating fuel injection. In
the injecting position, fuel may flow from control chamber 106 to
tank 28 via a restricted orifice 121, central bore 100, and fuel
outlet 104. As fuel from control chamber 106 drains to tank 28, the
upward force at hydraulic surface 114 may urge needle valve element
58 against return spring 90, thereby opening orifices 80 and
initiating fuel injection into combustion chambers 22. When
de-energized, return spring 123 may return armature 118 and control
valve element 120 to the non-injecting position.
The timing and level of the induced current within windings 116 may
be controlled to affect fuel injection. For example, as illustrated
in the control diagrams of FIGS. 3A and 3B, a first current level
may be induced within windings 116 at time T1 to initiate movement
of control valve element 120 toward the injecting position. The
current level at time T1 may be induced by applying a boosted
voltage to windings 116 that is at a level above a battery output
voltage associated with engine 10. The voltage used to induce the
first current level may be boosted through the use of a capacitor
circuit (not shown) that raises the current to a sufficiently high
level, thereby overcoming the effects of inertia. At time T2, a
second current level may be induced within windings 116 that
continues to move control valve element 120 toward the injecting
position. Because control valve element 120 is already in motion at
time T2, the second current level may be lower than the first and
induced by applying a voltage at or near the battery output level
associated with engine 10. At time T3, a third current level may be
induced within windings 116 to counteract the tendency of control
valve element 120 to bounce upon reaching upper seat 122 during
movement toward the injecting position, and to overcome hydraulic
inertia of the fuel in contact with control valve element 120. The
third current level may be less than the second current level. At
time T5, after the tendency of control valve element 20 to bounce
has decreased, the current may be further reduced to a fourth or
hold-in level that continues for the duration of fuel injection
until time T6. The fourth current level may be high enough to
overcome the force of return spring 123 and hold control valve
element 120 in the injecting position. Each of the current levels
from the first through the fourth may be less than the previous
current level to conserve energy and to reduce the cooling
requirements of solenoid actuator 59 while meeting the force
requirements of control valve element 120. At time T6, the hold-in
current level may be reduced to about zero to allow return spring
123 to move armature 118 and control valve element 120 to the
non-injecting position. For the purposes of this disclosure, the
combination of current levels induced within windings 116 to
produce a single injection event may be considered a current
waveform.
A current waveform associated with an exemplary injection event may
also include dampening current levels. In particular, controller 53
may induce a fifth current level within windings 116 at time T7 to
dampen or slow the movement of control valve element 120 prior to
control valve element 120 reaching the injecting position (e.g.,
prior to time T8). The induced current may be of an appropriate
level between zero and the current level at time T2. Dampening the
closing movement of control valve element 120 just prior to time T8
may reduce the likelihood of control valve element 120 bouncing off
of a lower seat 124. It is contemplated that instead of controller
53 inducing a fifth current, control valve element 120 may
alternatively enter a freewheeling mode of operation where the
kinetic energy of control valve element 120 is converted to
electrical energy directed away from solenoid actuator 59
(freewheeling induced current indicated with a dashed line in FIG.
3A, between time T7 and T8). The conversion of kinetic energy to
electrical energy may function to dampen the movement of control
valve element 120 in moving from the non-injecting position to the
injecting position.
The current levels induced within windings 116 may be adjusted to
dampen the movement of control valve element 120 toward the
non-injecting position between time T3 and T4. In particular, the
current level induced within windings 116 may be reduced just prior
to control valve element 120 reaching upper seat 122 to decrease
the likelihood of control valve element 120 bouncing away from
upper seat 122 and to lessen the effects of the associated
hydraulic inertia. The current level immediately following time T3
may be reduced to an amount sufficient to dampen the movement of
control valve element 120 while allowing adequate time to induce
the third current level at time T4 (referring to the dashed line in
FIG. 3A, between time T3 and T4). Alternatively, if time allows, a
current level (not indicated) may be induced at time T3 that
reverses the direction of the previously generated magnetic field
to oppose movement of control valve element 120 toward the
non-injecting position, thereby increasing the amount of
dampening.
In addition to dampening the movement of control valve element 120,
operation of control valve element 120 in the freewheeling mode may
provide an indication of the relative positions between control
valve element 120 and lower seat 124. In particular, the time
during which the current generated from the movement of control
valve element 120 toward the non-injecting position may be measured
during each movement cycle of control valve element 120. These time
measurements may then be averaged to determine an approximate
amount of time that it takes for control valve element 120 to move
from the injecting position to the non-injecting position. It is
noted that this average time may change depending on the previous
injection duration, the time before the next injection, the
injected amounts, and any other injection-related characteristics.
An elapsed time may then be compared with the average amount of
time to determine a distance remaining between control valve
element 120 and lower seat 124 or a time remaining before control
valve element 120 engages lower seat 124.
The relative position between control valve element 120 and lower
seat 124 may be used to trigger the current induced within windings
116 that dampen the movement of control valve element 120 toward
the injecting position. In particular, controller 53 may be
configured to initiate and terminate the induced current intended
to dampen the movement of control valve element 120 toward the
injecting position before control valve element 120 reaches lower
seat 124 in order to minimize the likelihood of a return bounce
caused by the dampening current. For example, if the previously
averaged time required for control valve element 120 to move from
the injecting position to the non-injecting position is 350 .mu.s
and the desired dampening duration is 100 .mu.s, controller 53 may
induce the dampening current at 250 .mu.s or earlier after control
valve element 120 has left the non-injecting position to prevent
control valve element 120 from return bouncing away from lower seat
124 as a result of the dampening current.
FIGS. 4 and 5 illustrate exemplary methods of operating control
system 35. FIGS. 4 and 5 will be discussed in detail below.
INDUSTRIAL APPLICABILITY
The fuel injector control system of the present disclosure has wide
applications in a variety of engine types including, for example,
diesel engines, gasoline engines, and gaseous fuel-powered engines.
The disclosed fuel injector control system may be implemented into
any engine where consistent fuel injector performance and
efficiency are important. The operation of control system 35 will
now be explained.
As indicated in a flow chart 200 of FIG. 4, controller 53 may
initiate a first injection of fuel into combustion chambers 22 of
engine 10 (referring to FIG. 1) by applying a first waveform to
solenoid actuator 59 (step 205). Injecting with the first waveform
may include, for example, sequentially inducing current levels one
through five as time progresses from T1 to T8 during an injection
event (referring to FIGS. 3A and 3B). Specifically, the first or
boosted voltage-induced current level may be induced within
windings 116 to overcome the effects of inertia and initiate
movement of control valve element 120 away from lower seat 124
during time T1 to T2. The second or battery-induced current level
may be induced within windings 116 to continue movement of control
valve element 120 toward the injecting position during time T2 to
T4, after the inertial effects of accelerating control valve
element 120 from a stopped position have diminished. The third or
bounce-reducing current level may be induced during time T4 to T5
to hold control valve element 120 at the injecting position while
overcoming tendencies for control valve element 120 to bounce away
from upper seat 122. The fourth or hold-in current level may be
induced within windings 116 during time T5 to T6 to hold control
valve element in the injecting position at a reduced energy
consumption level. Following time T6, the current level may be
reduced to about zero to allow for the return of control valve
element 120 to the non-injecting position. At time T7, the fifth
current level may be induced within windings 116 to dampen the
return of control valve element 120 to the non-injecting
position.
Following the first injection, controller 53 may determine if a
second injection event in a series of injection events is
close-coupled (e.g., the time duration between the end of the first
injection event and the start of the second injection event is less
than a predetermined amount) (step 210). If the second injection
event in a series of injection events is not close-coupled, the
second injection event may be implemented in an identical manner to
the first injection event by applying the first waveform to
solenoid actuator 59.
However, if the second injection event is close-coupled, controller
53 may instead apply a second waveform to solenoid actuator 59.
Specifically, in order to overcome the inertial effects of control
valve element 120 returning to the non-injecting position and any
associated bouncing, the first and/or second current levels of the
second waveform may be increased from the current levels of the
first waveform. In addition, because of the lack of time between
the first injection event and the desired second close-coupled
injection event, the application duration of the first one and/or
two current levels of the second waveform may be reduced from the
first waveform (step 220).
Following the second injection event in the series of injection
events, controller 53 may again determine if a subsequent injection
event is close-coupled (step 230). If the subsequent injection
event is not close-coupled, controller 53 may return to injection
using the first waveform. However, if the subsequent injection
event is close-coupled, controller 53 may inject using the second
waveform (step 240).
As illustrated in a flow chart 300 of FIG. 5, and as described
above, controller 53 may either implement freewheel dampening or
controller-induced dampening during the return movement of control
valve element 120 to the non-injecting position. Specifically,
controller 53 may determine an amount of required dampening by
comparing the time between T6 and T7 (referring to FIGS. 3A and
3B), or between the end of the fourth applied current and the start
of the dampening current (step 305) within a single waveform.
Controller 53 may then determine if the required dampening is less
than a predetermined dampening amount (step 310). If the time
between T6 and T7 is so short that dampening occurs too early
during the return of control valve element 120 to the non-injecting
position, a controller-induced current may be generated within
windings 116 to slow control valve element 120 before it returns to
lower seat 124 (step 330). However, if the time between T6 and T7
is sufficiently long, freewheel dampening may be implemented (step
320)
Because control system 35 can implement waveforms having multiple
hold-in current levels, the tendency of control valve element 120
to bounce and the energy consumed during an injection event may be
reduced. Specifically, because control system 35 can implement the
third current level after time T4 when control valve element 120
has reached the injecting position, the likelihood of control valve
element 120 bouncing away from upper seat 122 may be reduced. In
addition, because control system 35 may reduce the current level
induced within windings 116 to the fourth current level after time
T5, when the likelihood of bouncing has been reduced, the amount of
energy consumed during the injection event may be less than if the
current level had remained at the higher third current level.
Further, because control system 35 can modify the waveforms when
sequential injection events are close-coupled, the performance of
fuel injectors 32 may be increased. In particular, because
close-coupled injection events have different current level and
duration requirements than injection events that are not
close-coupled, these differences must be accommodated to produce
consistent injections of fuel. Controller 53 may accommodate these
differences by increasing the current level and decreasing the
current duration of the subsequent close-coupled injection
event.
In addition, because control system 35 implements dampening of
control valve element 120, the components of fuel injector 32 may
experience less wear and the performance of fuel injectors 32 may
be improved. Dampening of the movement of control valve element 120
prior to impact with upper or lower seats 122, 124 may reduce the
force of the impact and the likelihood of bouncing away from the
seat. The reduction in force may result in increased component
life. Further, reducing the likelihood of bouncing can improve
injector consistency.
It will be apparent to those skilled in the art that various
modifications and variations can be made to the control system of
the present disclosure without departing from the scope of the
disclosure. Other embodiments will be apparent to those skilled in
the art from consideration of the specification and practice of the
control system disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope of the disclosure being indicated by the following
claims and their equivalents.
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